No letter could be found about account deletion. So perhaps the best to do: use the link to write them an email or ring them, requesting deletion of your account.
By the way, your account will also be terminated in case of violation of their Terms. So be careful what you do, definitely if you have a paid account.
UPDATE: apparently you can get your account deleted using a trick suggested by one of our visitors. Read the comment below.
URLS:
http://www.rapidshare.com
https://www.rapidshare.com/#!help/rapidshare-ag_contact
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.